mongodb count num of distinct values per field/key

Question

Is there a query for calculating how many distinct values a field contains in DB.

f.e I have a field for country and there are 8 types of country values (spain, engl

Answer 1

I use this query:

var collection = "countries"; var field = "country"; 
db[collection].distinct(field).forEach(function(value){print(field + ", " + value + ": " + db.hosts.count({[field]: value}))})

Output:

countries, England: 3536
countries, France: 238
countries, Australia: 1044
countries, Spain: 16

This query first distinct all the values, and then count for each one of them the number of occurrences.